Method for producing titanium concentrates



United States Patent METHOD FOR PRODUCING TITANIUM CONCENTRATES David L.Arrnant, Metuchen, N. J., and Harold S. Sigurdson, Indianapolis, Ind,assignors to National Lead Company, New'York, N. Y., a corporation ofNew Jersey No Drawing. Application March 10, 1955, Serial No. 493,611

5 Claims. (Cl. 75-1) This invention relates to titaniferous compositionsof matter which react readily with strong mineral acids,

"particularly sulphuric acid, and to methods for preparing the same.This application is a continuation-in-part of our application Serial No.257,978, filed November 23, 1951, now abandoned.

Industrial processes for the preparation of titanium dioxide pigmentsdepend, in the first instance, upon a reaction between aniron-containing titaniferous material, ilmenite ore and strong sulphuricacid. By means of this reaction which, in the trade, is generally termeddigestion or attack, the titanium and iron values, among others aresolubilized. The iron values play no important role in the process andare almost invariably removed after dissolution, as by crystallization.However, in the digestion reaction they consume valuable acid which addsto the cost of producing the finished product.

Consequently, interest has developed in titaniferous compositions suchas slags which contain a higher proportion of titanium than is usuallypresent in ilmenite and relatively lower proportions of constituentslike iron which consume valuable acid. Such slags are produced bysmelting titaniferous ores in the presence of various fluxing agents,and usually contain appreciable amounts ofacid-consurning constituentssuch as FeO, CaO, MgO, SiOz and A1203 in addition to TiOz. Variousmethods for producing fluid slags from titaniferous ores have beensuggested in the past. In general these have been methods for forminglow-melting-point titanates such as sodium titanate or high iron contentiron magnesium dititanate, (Fe, Mg)O.2Ti02, or mixtures of suchtitanates to obtain eutectics between the titanate phases. In suchprocesses the titanates ordinarily constitute the major part of the slagcomposition. The silicate phase in these titanate slags is onlyincidental in obtaining low-melting, fluid slags. Although theseprocesses are successful in removing the greater portion of the iron inthe ore as useful metallic iron and may produce slags which are amenableto sulfate digestion, they suffer from the disadvantage that acidconsuming constituents are added to the TiOz, thus partially off-settingthe advantages of such processes. Moreover, it has been found that slagsprepared from certain titanium bearing ores which contain appreciablequantities of aluminum and silicon, do not digest satisfactorily instrong sulphuric acid due to the formation of bulky aluminum and siliconcompounds which prevent the reaction of sulphuric acid and the titaniumvalues from taking place in the normal manner.

The'present invention provides methods for the preparation of noveltitaniferous compositions using only moderate quantites of fluxingagents, which compositions are readily digestible in strong sulphuricacid, relatively high in titanium content, and relatively low in acidconsuming constituents such as FeO, MgO, CaO, A1203, SiOz, K20 and NazOand are therefore especially suited for the economic preparation oftitanium dioxide pig-, merits.

2,304,384 Patented Aug. 27, 1957 The principal object of the presentinvention is there fore the preparation of compositions or concentratesfrom titaniferous ores, which concentrates are rich in titanium andrelatively poor in FeO, CaO, MgO, A1203, SiOz, K20 and NazO and arereadily digestible in strong sulphuric acid. Another object of thepresent invention is the preparation of slag compositions which whenmolten are not viscous and flow freely.

A still further object is to produce readily digestible titaniumconcentrates which do not contain excessive quantities of fluxingagents. These and other objects of the invention will be apparent fromthe following more complete description:

The compositions of the present invention are characterized broadlyfirst as being readily digestible in strong sulphuric acid, the termreadily digestible being hereinafter defined, second, as having a smallcontent of unreduced iron (iron oxide, FeO) but appreciably less totaliron than contained in the original titaniferous iron starting material.a

For the purposes of the present invention, the term readily digestibleindicates a composition which, when subjected to a test, the conditionsof which are about to be described, gives a yield of solubilizedtitanium, calculated as TiOz, of at least of the total titanium content(TiOz basis) of the composition.

TEST FOR DIGESTIBILITY Ten grams of comminuted titaniferous material ofsuch fineness as to pass through a 325 mesh screen are heated in an ovento C. Sulphuric acid of at least 85% strength, in an amount sufiicienttheoretically to combine with the base-forming elements, e. g. PeO, MgOand CaO in the material, and in addition to provide a ratio of H2804 toTiOz of 2.0 (assumed 96% solubilization of all reactable constituents)is weighed into a large test tube and heated, preferably by means of asand bath, up to C. to C. The hot comminuted titaniferous material isthen quickly poured into the heated acid and the whole is thoroughlymixed. Reaction starts promptly and the temperature rises rapidly 30- 50C., and then slowly falls. When the digestion mass in thetest tubebegins to thicken, the test tube is placed in an oven at 170 C.-l90 C.and left there for two hours in order to dry out or cure the digestioncake. The cured cake is then dissolved in water or weak sulphtiric acid.The content of dissolved TiOz is determined by conventional analyticalprocedures.

The titaniferous compositions described in the appended claims asdigestible in strong sulphuric acid when subject to the foregoing testwill show yields of solubilized TiO2 of at least 80%. Preferredcompositions will give yields of 90% and higher.

Compositions having the foregoing characteristics are obtained by theprocess of the instant invention which comprises forming a mixturecomprising a titaniferous iron ore containing from 8% to 65% TiO2, saidmixture also comprising an oxidic compound of silicon, an oxidiccompound of aluminum, an oxidic compound of sodium, and/or potassium anda carbonaceous reducing agent. The mixture is heated to form molten ironmetal and a titanium slag. The molten iron and titanium slag areseparated from one another and the slag portion acidleached with dilutesulphuric acid to produce a digestible titanium concentrate. It has beenfound that the Foo content in the slag before acid-leaching may bepresent in an amount from 2% to 20%. The amount of fluxing agentspresent in the mixture should be sufficient to produce a slag in whichthe .sum of the is from 0.75 to 2.2 parts for each part of TiO2, and in*K20 -Al20s 3SiO2 Such a slag is then acid-leached with dilutesulphurieacid to remove the silicon, aluminum and sodium acid-solublecompounds thus leaving a TiO2 enriched slag concentrate. The titaniumstarting material used in the process of this invention preferably is atitaniferous iron ore. T ia taniferous iron ores of various types havebeen employed. The titanium contents of such ores vary widely, and orescontainingas low as 8% TiO2 and as high as 65% TiOg have been employedwith equal success. Ores contain? ing small amounts of TiO2 which areparticularly adaptable are those of the. magnetite-ilmenite andhematiteilmenite type, while ores containing higher amounts of TiO2 arethose of the ilmenite type.

Substantially all titaniferous iron ores contain various amounts ofsilica and alumina. It has been found by the process of the instantinvention, however, that when the ratios and total contents of oxidiccompounds of aluminum, silicon and sodium and/or potassium in the chargeare properly adjusted, substantially all of the silicon and aluminumconstituents in the ore are converted to a form which permits a freeflowing and fluid slag to be obtained during the heating step and inwhich moreover these aluminum and silicon constituents are readilysoluble in dilute sulphuric acid, and consequently readily removedduring the subsequent leaching operation. By the term oxidic compoundsof aluminum, silicon, potassium and sodium it is meant to includeoxides, carbonates, hydroxides and other compounds which form oxidesupon heating.

The fluxing agents to be employed may be added as chemical compounds oras natural minerals, such as feldspars, nepheline and the like.

It has been found that if the amounts of oxidic com pounds of aluminum,silicon and sodium land/or potassium are adjusted in the mixture tofallwithin certain specified limits, the titanium values will remain in aninsoluble form during a dilute acid leaching operation, while a largeportion of the silicon, aluminum, potassium and sodium and alsosubstantial amounts of the iron, calcium and magnesium constitutentswill be solubilized. This process therefore provides means for theproduction of a titanium concentrate which is low in silica, alumina,lime, magnesium and iron.

It has been found that the process of the instant int vention should becarried out at temperatures between about 1300 C. and .1700 C. tosufficiently reduce the iron valuesin the titaniferous iron ore. It ispreferable, however, to carryout the smelting operation at tempera-vtures from 1300 C. to 1500.C. Higher temperatures may be employed butcareful operation is necessary to avoid excessive reduction of the ironvalues and even the titanium values as well as excessive losses of thesoda values. using the fluxing agents previously described, a fluid,free-flowing slag is produced and both the silica and aluminaconstituents in the ore are fixed in the slag in a form in which theymay. be readily solubilized during. a subsequent acid leachingoperation. I

In carryingout the process of the instant'invention the titaniferousiron ore is admixed with the proper By smelting within the temperaturerange and amounts of timing agents and with a carbonaceous reducingagent, such as e. g. powdered carbon, coke or coal. '5 The amount ofcarbonaceous reducing agent to be employed should be suflicient toreduce substantially all of the iron oxide values to metallic iron. Themixture is then heated to a temperature between 1300 C.- 1700 C. untilthe iron content remaining in theslag portion is between 2.-20% FeO., I

In forming the mixture of the titaniferous iron ore and the fiuxingagents it is necessary to have present in the charge sufficient oxidiccompounds of silicon, aluminum and sodium and/or potassium, includingthose already present in the ore, to produce a slag which contains foreach part of TiO present in the slag from 0.75-2.2 partsSiO2+Al2Os+Na2O+0.66 K 0, and these fluxing agents should be present inproportions such that the SiOz is from 40-55%, the A1203 from 20-35%.and the Naz0+0.66 K20 from 20-30% of the total SiOz-I-AlaOs +Na2O-l-0.66K20.

Since sodium or potassium may be employed either singly; or together inconjunction with the silica and alumina values as fluxing agents in theprocess of the instant invention, it is convenient to express the K20values as Na2O since both the sodium and potasvalues may replace oneanother on a mole basis. In order to express the K 0 on a Na2O weightbasis, the percentage ofKzO multiplied by the factor 0.66 gives the Na Oequivalent on a weight basis. Whether sodium or potassium are used aloneor in combination with one another, the sodium and potassium values willhereinafter he expressed as the sum of Na2O+0.66 K20. This sum shouldliesomewhere between about 20% and 30% a the method previouslydescribed.

In slag ging operations it is difficult to maintain all of the sodium oripotassium values in the mixture as the sl gg ng operation proceeds.Usually a portion of the sodium or potassium content added as a fluxingagent-is volatilized during the heating operation and therefore aportion is lostfrom the system. The amount of sodium or potassiumcontent lost during the operation may vary widely with'the individualfurnace used. necessary to take this loss factor into account whendetermining the amount of fluxing agents to be employed in the instantsmelting operation. By minimum experimentation it is simple to determinethe amount of sodium or potassium loss on the particular furnace to beemployed and such loss is then compensated for in subsequent smeltingruns.

In carrying out the acid-leaching operation, it has been found thatsatisfactory results have been obtained when dilute sulphuric acid isemployed. The strength of sulphuric acid used preferably should be from5% to 15%. The amount of sulphllIiC acidemployed in the leachingoperation should be in at least slight excess over the amount requiredto react with all of the sodium, aluminum and silicon constituents andbetween 30% and 60% of the Fe, Ca and Mg constituents. It is preferredto carry out the leaching operation at'temperatures from 25 C. to C. Theparticle sizeof the slag may vary from minus 20 mesh to, substantiallyall minus 325 mesh. By earryingtout the leaching operation Within thepreferred limits previously given it has been found that efficient It istherefore leaching of the aluminum and silicon constituents will beobtained with a minimum of loss of titanium values.

In order to more fully illustrate the instant invention the iollowingexamples are presented to show typical operations employing varioustypes of titaniferous iron ores using various amounts of fiuxing agents.

Example 1 100 parts of ilmenite ore were dry blended with 23.2 parts ofSiOz, 13.0 parts of A1203 and 15.0 parts of Na2O, and 12 parts of coke.The ore had the following analysis on a weight percent basis:

TiOz 58.4 FeO 12.0 Fe2O3 24.7

CaO 1.0 S102 1.8 A1203 1.2

MgO 0.9

The above mixture was charged into an arc furnace, heated to 1500 C. andheld at that temperature for 1 hour. The molten iron and the slag wereseparately tapped from the furnace. The slag produced was fluid andfree-flowing.

The cooled slag was ground to substantially all minus 325 mesh (2% +325)and analyzed. The slag had the following analysis:

T102 51.3 FeO 2.6 N220 9.0 CaO 1.1 S102 20.0 A1203 15.6 MgO 0.4

It should be noted that the FeO content of the slag was 2.6% and foreach part of T102 present in the slag there were .87 part ofSiO2+A12O3+Na2O.

The ground slag Was then leached in sulphuric acid for one half hour at75 C. with rapid stirring and leach liquor was removed from the leachedslag by filtra- The leached slag was then digested in 89% sulphuric acidaccording to the digestion procedure given above and a TiO2 recovery of94.5% of the titanium values in the slag was digested and recovered assoluble titanium sulphate.

Example 2 Another slag was prepared using a titaniferous iron ore havingthe following analysis:

FeO 34.3

FezOs 33.6 CaO -2 0.6

parts of this ore were mixed with 5.45 parts ofSiOz, 6.00 parts of NazOand 15 parts of coke. The mixture was processed according to proceduredescribed in Example 1 and the results are recorded in Table 1.

Example 3 Another slag was prepared using another type of ilmenite whichhad the following analysis:

TiOz 40.3 FeO 28.6 Fe2O 19.1 CaO 1.0 SiOz 3.8 A1203 3.9 MgO 3.3

100 parts of this ore were blended with 11.8 parts of Si02, 5.0 parts ofA1203, 11.0 parts of Na2O and 13 parts of coke. The mixture wasprocessed according to the procedure described above and the results arerecorded in Table 1.

Example 4 Another slag was prepared using a titaniferous iron ore havingthe following analysis:

T102 19.5 FeO 30.4 Fe203 26.3 CaO 2.6 Si02 12.3 A1203 6.9 MgO 2.0

100 parts of this ore were mixed with 2.0 parts of SiOz, 8.7 parts ofNazO and 15 parts of coke. The mixture was processed according to theprocedure described in Example 1 and the results are recorded in Table1.

Example 5 Another slag was prepared using a titaniferous iron ore havingthe following analysis:

TiOz 9.5

FeO 32.1 F6203 48.4 CaO 0.6 S102 2.3 A1203 5.8 MgO 1.3

100 parts of this ore were mixed with 7.9 parts of SiOs, 7.2 parts ofNazO and 17.5 parts .of coke. The mixture was processed according to theprocedure described in Example 1 and the results are recorded in Table1.

Example 6 Another slag was prepared using the ilmenite ore shown inExample 1 in which more Na2O was added as' a fluxing agent. In thisexample 100 parts of the ore wereblended with 23.2 parts of S102, 13.0parts of A1203, 18.3 parts of Na2O, and 12 parts of coke. Themixture wasprocessed according to the procedure described in Example 1 and theresults are recorded in Table 1.

Example 7 Another slag was prepared using the titaniferous iron oreshown in Example 2 in which more $102 was added as a fluxing agent. Inthis example 100 parts of the ore were blended with 8.3 parts of SiO2,6.0 parts of N220 and 15 parts of coke. The mixture was again processedaccording to the procedure described in Exam ple 1 and the results arerecorded in Table l.

the ore were mixed with 33.4 parts of K2CO3, 13.0 parts of A1203, 23.2parts of S102 and 12 parts of coke. The slag produced was similar tothat obtained in Example 1. The results are recorded in Table 2.

Example 1 1 ployed in: Example 10. The results are recorded in Ta- 75TABLE 1' Exam le N 1 2 3 4 5 0 7 Slag Analysis (l erceutl:

T101" 1 51.3 47.5 51.4 33.4 28.6 49.0 40.1 t 2.6 2.7 2.5 3.0 3.0 4.5 9.41.1 2. 4 1. 3 5. 2 1. s 0. 9 2.3 0.4 4.1 4.2 4.0 3.9 5 0.7 3.7 15.0 12.711.4 13.5 17.5 12.3 9.9 20.0 20.0 19.9 24.3 30.7 20.1 23.3 9.0 9.2 9.311.0 14.5 12.0 10.3 1.3 Total... ..100.0 100.0 100.0 100.0 100.0 100.0100.0

R3515 111 Slag: s1ol+2;1o.+N'a.o; I I

moan-"4 0.87 0.88 0.79 1 1.29 2.19 0.92 1.11 Percent oi' flotalSlO1+AlzO1+ 310, Present as- '05-... 45 43 49 40 49 45' 53 7 o 35 30 2s1 27 2s 2s 22 Na, 20 22 23 24 23 27 25 Lcachlngconditlons:rereentmsorstrength. 10 10 10 10 10 10 10 Time, 1 1 1 1 1 Temp. 0... 7575 75 75 75 75 100 H18 ilsla Rate 0. 75 0.75 0. 75 1.0 1.2 o. 75 1.0

Analysis of Le'schedSlag'(Pei-cent):

Dlgestlbillty of Leeched Slag PeroentTlO'a'R'ecovery' 94.5 30.5 30.090.0 85.0 94.0 97.0

In the following example K is used to replace part TABLE 2 or all of theN220 employed in the previous examples.

Example No 8 9 l0 11 Exam le 8 1.

. p SlagAnalysis (Percent): T10; 42.3 43.2 7 Using the ore described inExample 2, 100 parts of 2' 0 211 0: 9 110 the ore were mixed with 5.5parts SiOz, 13.4 parts of f: 3-; K2CO3 and 15 parts of coke. 1 Themixture was processed 19:2 20:5 21:3 2017 according :to the proceduredescribed in Example 1 and KO 4D 1 14.9 7.1 13.0 0.9 the resultsarerecorded 11 Table 2. RatloinSlag:Sl0z+Al1Oa+Na10+0.66KzO:

Percent of Total (SlO1-i-Al1O;+Naz0+ V I 0.216510), Present 25- 47 on 149 1 l 1 5 Example 9 29 28 29 31 v I 24 22 20 20 Using. the oredescribed in Example 2,- 100 parts of 10 10 '10 10 the ore were mixedwith 6.8 parts of K2003, 5.1 parts of NazCOa, 5.5 partsof SiOz and 15parts of coke. After (175 processing in the same manner a fluid slag wasobtained 4,1 27.6 83.4 and theflresults are recorded in Table 2. 243 p2.2 2.1 1.2 1.1 5.9 5.1 1.0 0.9 it 3% 3'? 3'? Example 10 0Z4 010 K10 1.30.3 2.2 1.3 Dlfiestlbility of Leeched Slag, Percent T101 92 9 89 O 88 092 5 ecovery Using the ore described 1n Example 1, parts of I It hasclearly been shown by the description of the inthe addition of oxidiccompounds of silicon, aluminum.

and sodium and/or potassium as fluxing agents. The amounts of oxidiccompounds of aluminum, silicon and sodium and/or potassium added asfiuxing agents are 9 carefully controlled within specified limits inorder to convert the aluminum and silicon constituents in the ore to anacid-soluble form which in a subsequent acid leaching step may bereadily removed. Slags prepared using oxidic compounds of siliconaluminum and sodium and/ or potassium within the specified limits formfree flowing and non viscous slags.

Such free-flowing slags provideeflicient and effective separations ofthe slag and molten iron portions. Such slags are easy to handle andeconomical to process. The titanium concentrate formed according to theinstant invention contains only small amounts of residual iron, aluminumand silicon constituents thereby providing for a titanium concentratehigh in TiOz content.

While this invention has been described and illustrated by the examplesshown, it is not intended to be strictly limited thereto and othermodifications and variations may be employed within the scope of thefollowing claims.

We claim:

1. A method for producing a digestible titanium concentrate whichcomprises forming a mixture comprising a titaniferous iron ore whichcontains from 8% to 65% TiOz, said mixture also comprising acarbonaceous reducing agent, an oxidic compound of silicon, an oxidiccompound of aluminum, and a compound selected from the group consistingof oxidic compound of sodium, oxidic compound of potassium and mixturesthereof, heating said mixture to form a slag and molten iron at atemperature between 1300 C. and 1700" C. until the FeO content of saidslag is reduced to between 2% and 20%, the amount of oxidic compounds ofsilicon, aluminum and sodium plus potassium present in said mixturebeing sufiicient to produce a slag in which the sum of the Si02, A1203,and Na2O+0.66 K20 is from 0.75 to 2.2 parts for each part of TiOz, andin which the SiO: is from 40% to 55%, the A1203 is from 20% to 35% andthe Naz+0.66 K20 is from 20% to 30% of the totalSiOz-I-AlaOa-l-Naa0+0.66 K20 present in the slag, leaching said slagwith dilute sulphuric acid to remove the silicon, aluminum andsodium-l-potassium acid-soluble compounds, the titanium values remainingin insoluble form in said slag during said leaching operation andseparating the leach liquor from the leached titanium slag.

2. Method according to claim 1 in which the SiOz is from to the A1203 isfrom 24% to 30%, and the Naz0+0.66 K20 is from 22% to 28% of the totalSiO2+Al2O3+Na2O+0.66K2O present in the slag.

3. Method according to claim 1 in which said mixture is heated at atemperature of l300 C.1500 C.

4. Method according to claim 1 in which the slag is leached withsulphuric acid of strength between 5% and 15%.

5. Method according to claim 1 in which the slag is leached with diluteacid at temperatures between 25 C. and C.

References Cited in the file of this patent UNITED STATES PATENTS921,686 Fitzgerald et al. May 18, 1909 1,717,542 Rossi et al. Feb. 15,1916 1,343,441 Farup June 15, 1920 1,489,417 Bachman Apr. 8, 19241,618,795 Bachman Feb. 22, 1927 1,699,173 Whittemore Ian. 15, 19292,375,268 Wyckolf May 8, 1945 2,417,101 Campbell Mar. 11, 1947 2,445,377Wyckofi July 20, 1948 2,453,050 Turbett Nov. 2, 1948 2,471,242 RoysterMay 24, 1949 2,476,453 Peirce et al. July 19, 1949 2,631,941 Cole Mar.17, 1953 FOREIGN PATENTS 251,527 Great Britain May 6, 1926 OTHERREFERENCES Engineering and Mining Journal, April 1942, page 77.

1. A METHOD FOR PRODUCING A DIGESTIBLE TITANIUM CONCENTRATE WHICHCOMPRISES FORMING A MIXTURE COMPRISING A TITANIFEROUS IRON ORE WHICHCONTAINS FROM 8% TO 65% TI02, SAID MIXTURE ALSO COMPRISING ACARBONACEOUS REDUCING AGENT, AN OXIDIC COMPOUND OF SILICON, AN OXIDICCOMPOUND OF ALUMINUM, AND A COMPOUND SELECTED FROM THE GROUP CONSISTINGOF OXIDIC COMPOUND OF SODIUM, OXIDIC COMPOUND OF POTASSIUM AND MIXTURESTHEREOF, HEATING SAID MIXTURE TO FROM A SLAG AND MOLTEN IRON AT ATEMPERATURE BETWEEN 1300*C. AND 1700*C. UNTIL THE FEO CONTENT OF SAIDSLAG IS REDUCED TO BETWEEN 2% AND 20%, THE AMOUNT OF OXIDIC COMPOUNDS OFSILICON, ALUMINUM AND SODIUM PLUS POTASSIUM PRESENT IN SAID MIXTUREBEING SUFFICIENT TO PRODUCE A SLAG IN WHICH THE SUM OF THE SIO2, AL2O3,AND NA2O+0.66 K20 IS FROM 0.75 TO 2.2 PARTS FOR EACH PART OF TI02, ANDIN WHICH THE SI02 IS FROM 40% TO 55%. THE AL203 IS FROM 20% TO 35% ANDTHE NA20+0.66 K2O ID FROM 20% TO 30% OF THE TOTAL SI02+AL203+NA20+0.66K20 PERCENT IN THE SLAG, LEACHING SAID SLAG WITH DILUTE SULPHURIC ACIDTO REMOVE THE SILICON, ALUMINUM AND SODIUM+POTASSIUM ACID-SOLUBLECOMPOUNDS, THE TITANIUM VALUES REMAINING IN INSOLUBLE FORM IN SAID SLAGDURING SAID LEACHING OPERATION AND SEPARATING THE LEACH LIQUOR FROM THELEACHED TITANIUM SLAG.